Complex ester synthetic lubricants



United States Patent v CONIPLEX ESTER SYNTHETIC LUBRICANTS Alfred H. Matuszak, Westfield, N. J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application March 17, 1954, Serial No. 416,941

2 Claims. (Cl. 260484) This invention relates to synthetic lubricating compositions. Particularly the invention relates to new and useful synthetic lubricants that have outstanding utility at both high and low temperatures and that have, in addition, low carbonization characteristics and result in little or no sludge formation when used in automotive engines. More particularly, the instant invention relates to new and useful synthetic lubricating compositions which comprise the complex reaction products of mercapto or hydroxy acids, aliphatic carboxylic acids and organic hydroxyl containing materials.

In recent efforts to obtain superior lubricating compositions which have unusual and specific properties, there have been developed entirely new synthetic materials. In general, these new synthetic lubricants are characterized by viscosity properties that are outstanding at both high and low temperatures, especially when compared to mineral oils. These outstanding low and high temperature properties are especially desirable for use in equipment designed to operate over a great temperature differential, such as jet engines for aircraft use, combustion engines for aircraft and the like. It has been found that mineral lubricating oils are generally undesirable for the lubrication of these engines because of their high and low temperature viscosity limitations.

It has also been found that synthetic lubricants may be desirable for the lubricating of standard automotive engines. In addition to the versatility of their viscosities, the use of some types of the synthetic lubricants investigated have been found to result in very low rates of combustion chamber deposit formation, particularly when used for long periods of time. These combustion chamber deposits usually occur in the form of carbonaceous deposits on the. combustion chamber surfaces. of formation of combustion chamber deposits result in increased power factor from fuel, less increase in'the octane requirement of the engine, less pre-ignition'tendency, and a general overall improvement in engine operation. These new and improved lubricants may also serve to reduce, or remove, the combustion chamber deposits of engines already heavily loaded with such deposits.

It has been found that for use in reciprocating engines, particularly as a lubricant for automotive engines, a lubricating composition must meet several requirements. In order to form an effective lubricating film and to maintain that film at low and high temperatures, it must have certain viscosity characteristics. At low temperatures, the lubricant must be sufliciently labile to flow through the circulatory system of the equipment and allow movement of lubricated surfaces without undue power requirement.- A lubricant having an ASTM pour point below about +35 F. has sufiicient low temperature lability to make it satisfactory in these respects for general use. At high temperatures a lubricant must have suflicient body or thickness to furnish and maintain a satisfactory lubricating film. It hasbeen found that a lubri- Low rates 2,815,358 Patented Dec. 3, i957 cant that is satisfactory in this respect will have a viscosity at 210 F. of between about 2 and 60 centistokes or 32.8 and 280 Saybolt Seconds Universal. To prevent undue lubricant loss, due to volatility and general molecular disintegration, and to insure against explosion hazards at hightemperatures sometimes encountered, a lubricating composition should have a flash point in excess of about 300 F. These requisites are inherent in the term lubricating compositions, as used in this specification, and the materials of the invention are limited to those within these operable ranges. In general, the preferred materials, as contemplated herein and as described in the preferred embodiment hereof, will have an ASTM pour point below about 15 F., a flash point above about 375 F., and will have viscosities within the range of 2.6 to 15 centistokes, or 35 to 78 Saybolt Seconds Universal at 210 F.

It has now been found, and forms the object of this invention, that the viscosity requirements as outlined above for synthetic lubricants may be met by materials which may be described as complex esters in which the portion of the ester between the terminal groups comprises a combination of varying proportions of at least one mol of either hydroxyor mercapto-acid with a combining portion of a glycol and/ or a dibasic acid.

The materials that are utilized as starting materials for the complex esters of this invention are as follows:'

(1) Monohydric alcohols or mercaptans represented by the formula wherein X is oxygen or sulfur and wherein R is an alkyl group containing from 1 to 20 carbon atoms. (2) Aliphatic dibasic acids of the formula HOOC (CH COOH wherein x is a whole number, preferablyfrom 2 to 8.

(3) Dibasic acids of the formula wherein y is a whole number, preferably from 1 to 8, and X is either oxygen or sulfur.

(4) Glycols of the formula wherein n is a small whole number, preferably 2 to 5 and wherein y is anumber, preferably from 1 to 20.

(5 Monobasic acids of the formula RCOOH wherein Rv is an organic group containing from 1 to 20 carbon atoms, preferably an alkyl radical.

(6) Mercaptoor hydroxy-acids of the formula wherein R is hydrogen or an alkyl group containing from 1 to 10 carbon atoms, X is oxygen or sulfur, and wherein z is a whole number, preferably 0 to 12.

Using these starting materials it is possible to build compositions having the desired lubricating characteristics. Some of the preferred types of contemplated complex esters are depicted by the formulas below:

acid-glycol-hydroxy acid-dibasic acid-alcohol a id-gly l-hydroxy.

acid-glycol-hydroxy propyLn-butyl, iso-butyl, sec.--butyl;.tertebutylpnsamyl,

isofamyl, n-hexyl, isohexyl, 2-.ethyl-1 hutyl; Z-ethyl-lhexyl, octyl, iso-octyl,- 2 octy1, iso-nonyl,. decyl, lauryl, tetradecyl, pentadecyl, octadecyl, ally1,- crotyl, oleyl, theterpineols, the C to,C Oxo alc,ohols-,-,alcohols derived from the Synolfprocess, those-derivedsfromthe oxidation of; petroleum. fractions, those derived; from the.

Guerbet reaction, those derived. from, the hydration of olefins, those derived via. the- OxyP: synthesis, and mixtures of the-above... The correspondingmercaptans may also be used. Especiallypreferredare those alcoholsand mercaptans containing from 6 to 10 carbon atoms.

Particularly desirable alcohols for use in this invention are those highly branched chain aliphatic alcohols prepared by the"Oxo"'synthesis.- The Oxofsynthesis-may be described asbeingithe catalytic reactionof an olefin.

with carbon monoxide and hydrogen. The reaction occurs at temperatures inthe order-of-300400 F., at pressures in the range of about 1000 to 3000 p. s. i., in the presence of-a suitablecata-lyst;ordinarily a heavy-metal carbonyl such as cobalt carbonyl: Theresulting aldehyde is subsequently hydrogenated to;a primary;alcohol. This process is described in U. S. Patent No. 2,327,066 issued to Roelen in-1943.-

It has been found that particularlydesirable alcohols for the formation of the complex esters of this invention can be prepared by the, applicatiomof the Oxo synthesis to polymers and cop olymersof C and C monool-efins,

These monoolefins arereadily available in petroleum refinery streams, andprocesses for theipconversion to liquid copolymers have been worked'out by the art. One such process, known as U. 0.1 P} polymerization, consists of p n thc fiIi-cmtai nest am. iq id phas n.

contact with an acidpatalyst comprising phosphoric acid impregnated.onkieselguhr. Other -acidic cataylsts, such as phosphoric acid or copper phosphate impregnated on silica gel, sulfuricacid, Ericd1-,Craftscatalysts, activated clays, silica-alumina, copper pyrophosphate etc may be used. Suitableconditions whenemploying phosphoric acidcatalysts of the U. O. P-.= typearetemperatures of 300 F. to 500 F., pressures-from-250'to 5,000p. s..i. and feed stocks comprising refinery streams containing propylene. and mixed butylenes. Suitablefeedstocks, for example, may contain=from to 60'rnolpercent propylene. from 0:5 to 15 molpercent butylenes; andfrom 0.1to 10 mol percent isobutylene, the remaining being saturated hydrocarbons. Other suitable. feed stocks. -ar,e the dimer and trimer of isobutylene.

The preferred oxo alcohols employed in .this invention are thosehaying from 8 tocarbon; atomsderived from olefin copolymers having frornfl to .19, carbonatoms. In preparing these Oxo alcoholsthe.adesired olefin'fraction is segregated from the crude olefin polymer product by fractionation. l

The following table, for example, shows the;structure and percent composition of C 0x0 alcohols prepared rom. AC1: olefinstreamwhich. h dbeenfractionatedirom.

It williibe noted that: Oxoalcohols derived from the olefins. produced by C C4 polymerization are mostlymethyl substituted.

Dibasic acids operable in-the concept of this invention includethefollowi ngr oxalic, malonic, succinic; glutaric, adipic, pimelic, suberic, azelaic, sebacic, fumaric, maleic, itaconic, citraconic, diglycolic, thiodiglycolic, thiodipropionic, dithiodiglycolicand thelike. Especially preferred are those dibasic acids containingfrom 6- to- 10' carbon atoms.

Operable glycols include: ethylene, the various diols, suchas propane-, butane-, pentaneand-'hexane-diols, the various polyallcylene glycols such as polyethylene glycols andipolypropylene glycols, and*the like-.- Especially preferredare the=polyethylene glycols of the formula:

mortal-1M0) 11 wherein; n: is an integer-zfromx 2 ;to- 5 aandiwhere 1y) is; an

integerof from lito 20;

Operable-1. monobasio. acids: include: the following: formic,=.iacc.tic,- propionic;. butyric; 2-ethylbutyric, caproic, 2-ethyl:.;hexanoic,- caprylic pelargonic,: capric; lauric, myristic, oleic... stearic, methoxyrpropionic, ethoxyethoxyacetic, IHOHOQ-fithYl 'hexyl adipate,v mono-C Oxo-sebacate, acids rderived=from;alccholsby caustic fusion, acids derived from petroleum fractions by oxidation, and mixtures ofzthe above. Those acids containing'fromA 10:10 carbon .atomsare preferred.

Operable. hydroxyand iv mercapto-acids' include the following: hydroxy acetic (glycolic), hydroxy-butyric, hydroxy-caproic, hydroxy-caprylic, picnic: (lactic), beta-hydroxy-propionic, hydroxy-stearic, and; the corresponding mercapto acids, such as thioglycolic; etc:

The preparation of the=con1plex-esters of this invention mayrbe accomplished byeither, a one-stepora two-step technique;

It:w,ill:b,e,=;noted fromrexamination of-the various types of; thfii complex esters ontemplated: asLdeScribed above, that a these 'estcrs are terminated; or; stop ped, by, use

ofi a monoflmciional lmaterial, either an;.-alcoh'ol, mercap tan or an acid. In the two-step technique, the central alpha-hydroxy-proor body portion of the complex ester may be prepared in a first step by admixing the desired amount of the chosen reactants with a small amount of a catalyst and a water entrainer in a reaction zone. The catalyst may be any of the commonly known esterification catalysts, such as sodium acid sulfate, toluene sulfonic acid, sulfosalicylic acid; sulfuric acid, zinc chloride, etc. The reaction temperature is maintained at about 150 to about 220 C. for from 2 to 6 hours, or until tests of the reaction mixture show that the esterification is substantially completed. In the second step, the stopping or terminating agent, either a monobasic acid or a monohydric alcohol or mercaptan is added in the correct amount. The reaction temperature is then maintained at about 200 to about 230 C. until such time that the neutralization number of the reaction product is at the desired low level.

However it may also be desired to prepare a half ester of a bifunctional material and then connect two moles of such half ester with a second bifunctional material. For example, the first step of such a procedure might be to react together molar quantities of an alcohol and a hydroxy acid in a first step and then react together two moles of such ester with a dibasic acid in a second step. Other variations available will be apparent to those skilled in the art.

Purification of the complex ester is accomplished by stripping off any unreacted ingredients, water entrainer, light ends and the like by a stripping step.' Vacuum stripping may be desired in some instances. The material, stripped as above, may then be washed'to remove any residual acidity with an alkaline solution, such as a sodium carbonate solution, etc. Final acidity may also be reduced to the desired level by filtration through alumina or charcoal or some similar adsorbent material.

In the one-step process, referred to above, the theoretical amount of all the desired reactants plus any excess are added to the reaction zone and the temperature maintained at about 190 to 230 C. for a period of time sufiicient to obtain a product of the desired low neutralization number. The same general finishing procedures as outlined above may be used to prepare the final product, that is, a stripping step, using vacuum if desired, a Washing step, and an alumina or charcoal treatment.

It may also be desired to add antioxidants to the esterification reaction or at other points in the process of preparing these complex ester synthetic lubricants. Such materials as phenothiazine have been found to aid in the preparation of more desirable lubricants.

The invention will be more clearly explained by reference to the following illustrative examples.

Example I.-Preparatin of type complex ester (Z-ethylhexanol-sebacic acid-glycolic acid-polyethylene glycolsebacic acid-Z-ethylhexanol) In this preparation a one-step procedure was employed. The following ingredients were charged to a 3-1 esterification apparatus equipped with stirrer, thermometer, reflux condenser and Water trap.

These ingredients were heated to reflux temperature and after 3 hours the temperature had gradually increased to 210 C. and 187 cc. of water had collected. The crude ester was then heat treated at 235 C. for 3 hours during which time the pressure was lowered to 10 mm.

to remove the volatile constituents. After washing with 10% Na CO aqueous solution and alcohol, followed by two water washes, the material was filtered and then stripped to 162 C. at 8 mm. to give 1140 g. of lubricant having the following properties:

Viscosity, cs., F.:

0 4,350 40 94,400 V. I 139 Pour point, F 45 Flash point, F 530 Fire point, F 570 1 hr. SOD lead corrosion loss, mg 61 SAESOD load test, lbs. -3 700 1 SAE lubricant tester is run in at 50 1b. load for 2 minutes, then load is increased manually by 50 lbs. every 10 seconds until scu fling of bearing rings occurs.

Example II.-'Preparati0n of type 1 complex ester (C 0x0 alcohol-glycolic acid-sebacic acid-glycolic acid-C 0x0 alcohol) The following ingredients were used:

G. Sebacic acid 202 Glycolic acid (70%) 218 C 0x0 alcohol (by oxonation and hydrogenation of tripropylene) 316 10% excess C Oxo alcohol 32 Heptane 57 NaHSO catalyst (0.5%) 3.0

ties: 1..

Kin. vis., cs.:

210 F 7.32 100 F 46.25 0 F 2,520 40 F 51,100 V. I Pour point, F 45 Flash point, "P 510 Fire point, F 560 It is also Within the concept of this invention to prepare synthetic lubricating compositions which comprise blends of the complex estersynthetic lubricants as described above with various of the additive materials used by the art to enhance special lubricating characteristics of the final blend. For instance, it is contemplated to blend with these complex esters viscosity index improvers such as polybutene, polyacrylate and polymethacrylate esters containing from 8 to 18 carbon atoms in the alcohol groups and other types. It is also contemplated to blend with these complex esters pour point depressants such as Wax naphthalene condensation products, acrylate and methacrylate ester polymers, fumarate vinyl ester copolymers and the like. Other additives, such as detergent inhibitors, anti-rust agents, extreme pressure additives, oxidation inhibitors and the like are also compatible with these synthetic esters and blends containing them are contemplated.

The synthetic lubricants of this invention may also be used to compound various blends using as a blending agent other synthetic lubricants such as formals, polyalkylene ethers, dibasic acid esters, silicones, silicates, polyglycol ethers, ether-esters, etc. The complex esters of this invention arealso;.compatible "with mineral oils of either naphthenic or paratfinic. origin and'blends'with thesematerials are contemplated.

The complex esters of this invention may also be used as the base oils for the formation of lubricating grease compositions. Greases from these esters may be prepared byv thickening them with any of the commonly used grease-forming soaps, such as the alkali or alkaline earth metalsoaps of high molecular weight fatty acids. -Soaps such as the oleates, stearates, or hydroxy stearates of sodium, potassium, lithium, calcium, barium, strontium and the like may be used. Soaps formed by heating animal, fishor vegetable oils with derivatives of the metals above may also be used.

To summarize briefly, the instant invention relates to newandimproved. synthetic lubricants of the complex ester type. These complex ester-s containfrom120 to 130 carbon atoms per molecule and are prepared by reacting a hydroxy or mercapto acid with amonofunctional and a difunctional compound selectedfrom the following classes of materials: monobasic acids, monohydric alcohols, mercaptans, glycols, and polybasic acids. The molecule will ordinarily be terminated by a monofunctional material, usually an alcohol, a mercaptan, or a monobasic acid and will contain at least one molecule of a hydroxyor mercapto-acid. The complex esters of the invention are preferably those having viscosities at 210 F. within the range of from 2.6 to centistokes, ASTM pour points below about 35 F., and flash points above about 300 F. Especially preferred and contemplated in the preferred embodiment hereof are those complex esters having the formula i i i i F i RXC(CH2)=CHXCR2GXCH(CH).AJXR4 wherein R, R and R arealkyl groups containing from 1 to carbon atoms, preferably 6 to 12 carbon atoms, wherein X is oxygen or sulfur, wherein z is a number from 0 to 12, preferably 4 to 6, R and R may be hydrogen or alkyl groups of from 1 to 6 carbon atoms and wherein-R, R R R ,-and'R are alkyl or alkylene groups containing from '1 to 20 carbon atoms, preferably from 6 to 12'carbon atoms, wherein R is selected from the group'consis'ting of hydrogen -or alkyl radicals containing from 1 to 10 carbon atoms, wherein X is oxygen or sulfur and wherein z is a number from '0 to 12, preferably 4 to 6.

What is claimed is:

1. A synthetic lubricating composition having an ASTM pour point below about 15 F., a flash point above about 375 F., and a viscosity at 210 F. between about 2.6 and 15 centistokes, which comprises a material of the formula:

0 o o nxii(ormiiixomwm xwnnho ,iiwnnziixn,

wherein R and R are alkyl groups containing from 6 to 10 carbon atoms, wherein X is selected from the group consisting of oxygen and sulfur, wherein x is a number from4 to 8, wherein y is a number of from 1 to 20, wherein z is a number of from 0 to 6, and wherein n is anumber of from 2 to 5, said material containing between about 25 and carbon atoms per molecule.

2. A lubricating composition according to claim 1 wherein R represents a branched chain alkyl group having about 8 carbon atoms, wherein X is oxygen, wherein x is 8,yis4,zis 0,andnis2.

References Cited in the file of this patent UNITED STATES PATENTS 2,260,295 Carruthers Oct. 28, 1941 2,271,856 Cummings Feb. 3, 1942 2,379,251 Muskat et al. June 26, 1945 2,559,510 Mikeska et al. July 3, 1951 2,573,701 Filachione et al. Nov. 6, 1951 2,608,577 Weesner Aug. 26, 1952 2,706,534 Hunter Apr. 19, 1955 

1. A SYNTHETIC LUBRICATING COMPOSITION HAVING AS ASTM POUR POINT BELOW ABOUT-15*F., A FLASH POINT ABOVE ABOUT 375*F., AND A VISCOSITY AT 210*F. BETWEEN ABOUT 2.6 AND 15 CENTISTOKES, WHICH A MATERIAL OF THE FORMULA; 